Marco: Welcome!
I think your experiences with Corona will depend largely on what you use it for. I think the SDK documentation tends to be very good and the performance also good (with some widget exceptions). The support for fixing bugs that you, as a developer, find tends to be pretty good (in my experience about 1-2 weeks to fix the tableview bug I reported last month, 1-2 weeks for the scrollview/tableview bug I reported, and about a week for the Nexus 6 status bar bug I reported last fall). Rob’s help in the forums as a Corona representative is invaluable.
If your app will rely heavily on UI components and standard user interaction, you will end up doing wheel recreation, possibly significant wheel recreation.
Every SDK or development platform has tradeoffs and weak spots. Corona’s weak spots that I’ve encountered are text handling, text input (though getting better in the last few months), and the work you’ll have to do to recreate native-ish UI components if your task requires it. Also things like not being able to share to Facebook on Android is frustrating – this discussion has been going on for nearly half a year without resolution: http://forums.coronalabs.com/topic/52755-can-corona-enable-limited-facebook-sharing-on-android-via-nativeshowpopup/ Or Instagram sharing on iOS via the share action sheet, which also is nonfunctional: http://forums.coronalabs.com/topic/53371-supporting-ios-modal-share-action-sheet-airdrop-print-add-to-home-screen-add-bookmark-add-to-reading-list-etc/page-2
If you don’t mind those weak spots, or they don’t affect you, I think you will enjoy lua and the community here.